In general, a construction machine such as a hydraulic excavator may be supplied with fuel directly from a fuel container such as a drum at a working site. In preparation for such a case, a traveling machine body in some such construction machines is equipped with a fuel supply pump (fuel pump or refueling pump). Some of these construction machines configured as follows are known: when a fuel supply pump is used for fuel supply, a sensor in the construction machine detects that the construction machine is full of fuel to allow the fuel supply pump to be automatically stopped (for example, Patent Documents 1 and 2).
At the working site, fuel supply may be performed in an adverse environment where, for example, dust flies around. In view of such a case, a strainer (filter) is provided to prevent foreign matter from being mixed into a fuel tank. However, if the strainer is clogged, fuel supply is delayed, degrading workability. Thus, some of the construction machines configured as follows are known: a sensor in the construction machine detects the pressure in the strainer, and when the detected pressure is equal to or higher than a predetermined value, it is determined that the strainer is clogged and the fuel supply pump is automatically stopped (see, for example, Patent Document 3).
Some other construction machines configured as follows are known: if the fuel container becomes empty during fuel supply and therefore the fuel supply is stopped, then the fuel supply pump runs idly and may be seized; to avoid this, a sensor which detects that fuel supply has been disrupted is provided, and when the sensor issues a signal indicating that fuel supply has been disrupted, the fuel supply pump is automatically stopped (see, for example, Patent Document 4).    Patent Document 1: Japanese Patent Application Laid-open No. 2000-264078    Patent Document 2: Japanese Patent Application Laid-open No. 2005-16332    Patent Document 3: Japanese Patent Application Laid-open No. 2011-173590    Patent Document 4: Japanese Utility Model Application Publication No. H7-13549
However, all of the above-described construction machines use a dedicated sensor for detection to automatically stop the fuel supply pump based on the detection, leading to an increased number of components. Furthermore, the sensor needs to be maintained, disadvantageously degrading workability and increasing costs. These are problems to be solved by the present invention.